Even if you find a hitch that will adjust down far enough to level the 5th wheel when towing, please remember you will still need to maintain a 6" minimum clearance between the trailer and the bed rails. Unless you have a tow body or flat be on the truck, you may need to raise the trailer or lower the truck suspension back to stock height.
Rick and Janice Binns
2006 MS 32TK3, Mor/Ryde Pin Box and I.S., Auto Level-Up
2012 Ford F450 6.7 L Diesel, air bags and 25K Reese Signature hitch (factory installed)